1. Field of the Invention
The present invention is the result of the work of Mr. Alain LE MEHAUTE employed by LABORATOIRES DE MARCOUSSIS, the research center of COMPAGNIE GENERALE D'ELECTRICITE, and of Mr. Alain PERICHAUD employed by UNIVERSITE AIX-MARSEILLE I.
The present invention concerns a composition based on an electron conducting polymer and its application to a positive active material for electrochemical generators.
2. Description of the Prior Art
There exist polymers featuring along their chain numerous double conjugate bonds and therefore liable to feature significant electron conductivity, which is not the general rule with polymers. This conductivity may be modulated by doping, by reducing or oxidizing the polymer and neutralizing the excess charges by means of a counter-ion which may be either an anion or a cation.
The electron conducting polymers include polyanilines, polyacetylene, polyparaphenylene, paraphenylene polysulfide, paraphenylene polyvinyl, polythiophene, polypyrrole, and substituted derivatives of these substances.
The specific energy of the active materials that can be produced from these polymers is on average less than 500 Wh/kg at three volts. There is known, for example, a secondary electrochemical generator of which the negative electrode is of lithium, the positive electrode of a doped polyacetylene the monomer of which has the formula C.sub.2 H.sub.2 (LiClO.sub.4).sub.0.3, and the electrolyte is lithium perchlorate in propylene carbonate. The voltage of a cell of this kind is 3.7 volts and the theoretical specific capacity and energy of the positive active mass are 139 Ah/kg, that is 516 Wh/kg and 206 Wh/liter, but after implementation as a generator the stored specific energy does not exceed 100 Wh/kg.
It is found in practice that active materials based on electron conducting polymers do not in the current state of the art offer any significant improvement over existing mineral materials; thus in primary generators these materials offer less performance than substances of the MnO.sub.2 or carbon fluoride type and in secondary generators it is found that the best results are obtained with mineral materials such as NiPS.sub.3, TiS.sub.2, MoS.sub.3 which all in practice exceed 200 Wh/kg.
An objective of the present invention is to provide a substance based on an electron conducting polymer offering performance characteristics very much higher than those of known materials and providing for the obtaining of positive active materials having a theoretical specific energy which may be in excess of 1 000 Wh/kg.